1. Field of the Invention
The present invention relates to a laser scanning microscope that can correct aberration and can change a focusing position of the objective lens.
2. Description of the Related Art
Recently, a laser scanning microscope that can acquire an image with higher quality is demanded; therefore, a laser scanning microscope that can correct aberration remained in an optical element (e.g., objective lens) focusing a light emitted from a light source on a sample has been used.
A microscope disclosed in JP-A No. H11-101942 (KOKAI) (U.S. Pat. No. 6,771,417) is known as an optical microscope that can correct the aberration of the objective lens. Specifically, in the microscope disclosed, a deformable mirror used as a wavefront modulator is arranged in front of the objective lens of the microscope. Then, the aberration in the microscope is corrected while shifting a focusing position of the objective lens by deforming a surface of the deformable mirror to modulate a wavefront of light.
The aberration is caused in the laser scanning microscope by a difference between a refractive index of a cover glass holding a fluorescent sample and a refractive index of the fluorescent sample itself, or by a difference between the refractive indices just mentioned and a refractive index of air, for example, especially when the fluorescent sample is observed. Furthermore, the sample might not be ideally illuminated with an illuminating light due to the aberration.
Further, when a focusing position of the objective lens is shifted by using the deformable mirror in the laser scanning microscope, a real NA (Numerical Aperture) of the objective lens is changed and a diffraction diameter of a laser beam at a confocal pinhole is slightly changed.
On the other hand, there is a problem that a focusing position is slightly deviated in a direction of an optical axis for each of the laser beams with different wavelengths due to color aberration of an optical system when a laser beam with one wavelength is switched to a laser beam with another wavelength.